Ensure virtualenv/pip are installed on centos
Ensure virtualenv/pip are installed on centos

This patch ensures virtualenv/pip are installed on centos using
distro packages, like it is in other distributions.

Change-Id: If3ac657e9a3e013a4013dd98b4cb785ef7ee9800

openstack/openstack-ansible-openstack_hosts,openstack/openstack-ansible-openstack_hosts